Some things that have worked well for me:
Like any other type of fishing, when conditions get tough I think downsize and fish deep and slow.
When they are picky but you can see them, get below the school, the deeper ones seem to be a bit more aggressive at times.
I prefer "stick" type jigs to yozuri's though at times when they are skittish and near the surface, the jap jigs really can work well(just not for me

).
Most of the time, the squid will hit on the drop. I was watching them the other night in the canal. They were cruising near the surface and for a while the bite was good, then it shut off. They were still there, just super picky. They would only take a jig(for me) if I let it drop on a slack line thru the school. I could watch them take off for it as it dropped and disappear in the depth.
Here is a huge key for me: I use 10# White braid, usually with a short mono leader. The reason for the white braid is that it is easier to see the line pause as a squid grabs the jig on the drop. It's usually just a slit second pause and if you aren't paying attention, they drop it.
This is key - carry different size and weight jigs and experiment until you get the sink rate right.